WASHINGTON – When a popular app that predicted Metro’s bus times mysteriously stopped working in December, many D.C. area commuters were left in the dark — and out in the cold — at bus stops.

NextBus DC, a widely used app that tracked when buses arrived, disappeared from the iTunes App Store when a contract ended between the NextBus DC developer and the company that provided the data for the app, the Washington Post reports.

Ken Schmier, the NextBus DC developer, told the Post he received 7,000 complaints about the suspended service and said he was working to re-launch the app.

But one local bus rider decided not to wait and took matters into his own hands.

Jason Rosenbaum used NextBus DC every day on the commute from his apartment in Adams Morgan to his job in downtown D.C., where he works as the director of technology at the Corporate Action Network, a nonprofit that supports campaigns working to expose corporate abuse.

In December, Rosenbaum, 28, thought the app was just experiencing glitches. When he realized NextBus DC was gone for good, he looked on the App Store for something similar.

“I couldn’t find one that hit all of the features I wanted, so I decided to make one,” says Rosenbaum, who recently developed BusTrackDC, an app that maps bus lines and predicts arrival times for Metrobuses.

Rosenbaum had never developed an app before, but says the process is similar to developing a website — something he does at his current job and has done in past work.

“I was using a technology I knew and kind of put it in an app wrapper,” Rosenbaum says. “I learned new programming languages and some new techniques, but a lot of it was some things I’m familiar with.”

“There are many third-party apps out there that work with our real-time data,” says WMATA spokesman Dan Stessel. “The data is provided to developers through an API that is then fed to apps.”

Rosenbaum says he took the data feed and used free tools to translate the information from the web platform he built to something usable for a mobile device. The then joined Apple’s developers program, which allowed him to put his apps on Apple’s iTunes App Store for a roughly $100 fee.

Since making BusTrackDC available to the public in early February, Rosenbaum says thousands of people have downloaded the free app.

Columbia Heights resident Nathan Karrel previously used NextBus DC and downloaded BusTrackDC in January after hearing about the new app from a friend.

Karrel, who has lived in D.C. for four years, uses it when attempting to go some place new or when traveling during off-peak hours. He says the app works well and is a good replacement for the former tool. However, he says he misses some of the features of NextBus DC, which is still not working.

“Rather than a collection of green dots on a map that you have to work through, it would be more helpful to have a list of bus routes with bus times integrated into the list view,” Karrel says. “It would also be helpful if you could save the bus routes that are used more frequently.”

Rosenbaum made the first major update to the app since its release. According to Rosenbaum, the new version he is launching Tuesday allows users to save stops as favorites for easy access. Rosenbaum says the “favorites list” was the most requested feature for the app.

Rosenbaum adds that his app has one feature that was missing from many Metro transportation apps — a route map for each line.

“If you’re at a stop, and a bus is coming down the block and you don’t recognize the line number, you can find out if that bus is going your way,” he says.

So far, Rosenbaum has received an encouraging response for the app based on users’ comments online.

“Looking at the reviews on the App Store, so far everything’s been very positive,” Rosenbaum says.

Stessel says WMATA does not test third-party apps, so it is incumbent on the user to check the reviews and ratings before purchasing BusTrackDC.

In the future, Rosenbaum hopes to collaborate with other developers to expand the features of the app. Users can share ideas and communicate with Rosenbaum on the BusTrackDC website.

Correction: An earlier version of this story stated NextBus DC predicted Metro train arrival times.